Automatic stop for electrically-driven machines



Feb. 24, 1931.

v. B. LOWDER 4, 82

AUTOMATIC STOP FOR ELECTRICALLY DRIVEN MACHINES Filed Oct. 22, 1929 gwwmtoz Ram/J67 111101112161,

Patented Feb. 24, 1931 PATENT oFrrcE VANDER IB. LOWDCER, CONCORD, NORTH CAROLINA AUTOIIYIAEIIG STOP FOB ELECTRICALLY-DRIVEN MACHINES Application filed October 22, 1929. Serial No. 401,592.

This invention relates to automatic stop systems for electrically driven machines, and more particularly for. cloth finishing ma: chines and the like, such for example as'dis- 6 closed in my prior Patent No. 1,7 03,7 7 4, dated by current of relatively high voltage, and as it is undesirable to employ such voltage on the feeler device for controlling the automatic stop mechanism, another object of the invention is to provide a transformer arrangement for stepping down the voltage to the desired extent, and to utilize such reduced voltagefor operating a relay.

In connection with automatic stop systems of this general character it is frequently desirable to be able to manually start and stop the motor at will independent of the automatic stop device. Still another object of the invention therefore is to combine with the above mentioned transformer and relay manually operated mechanism in the form of start and stop push buttons for opening and closing the main switch controlling the supply of current to the motor.

In order that the invention may be readily understood, reference is had to the accompanying drawing forming part of this specification and in which the single figure is a diagram showing the circuit connections which I prefer-to employ and conventionally illustrating the apparatus which is associated therewith.

Referring to the drawings in detail, l designates an electric motor connected in any suitable way to a cloth finishing or similar machine for driving the same. This motor may be of any suitable type, but as illustrated, it is shown as a three-phase alternating current motor fed from a supply circuit 2 in A which is' interposed a three-pole switch 8. 59 This switch is biased to open position, a

spring 4 being shown, tending to open the switch.

The switch-is arranged to be closed and held closed by electromagnetic means, illustrated as an electromagnet' 5 mounted adjacent the switch and included in a control ci; cuit 6, 7, the conductor 6 tapping the supply circuit at the point a, outside of the switch, and the conductor 7 extending to the push button switches hereinafter described. Additional control conductors 8 and 9, tapping the supply circuit at the points I) and 0, outside and inside of the main switch, respectively, are provided. The conductor 8 is connected to one side of the primary winding of a transformer 10, the other side of this winding being connected by a conductor 11 to a contact 12 engaged by the armature 18 of a relay, pivoted at 13, and normally held against the contact by means of a spring 18 This armature is shown as U-shaped, one leg engaging the contact 12 as described, and the other leg engaging similar contact 12. From this extends a conductor 14 to a contact point 15 forming part of one of the push button switches. A similar contact 16 forming part of the other push button switch is connected to the control conductor 9.

The push button switches comprise independently movable switch members 17 and 18, pivoted at 19 and 20 respectively. Push buttons 21 and 22 are shown as adapted to bear against and operate the respective switch members. A spring 23 normally holds the switch member 17 in engagement with the contact 15, and a similar spring 24 normally holds the switch member 18 out of engagement with the contact 16, as shown in the drawing.

The conductor 7, which is connected at one end to the electromagnet 5, is connected at the other end to a conductor 25 which isv united to pivot points 19 and 20 of the two switch members 17 and 18.

The above mentioned relay has a winding 26 disposed adjacent the armature 13 and one end of this winding is connected by a c011- ductor 27 to one side of the secondary winding of the transformer 10. The other end of the relay winding 26 is connected by conductor 28 to one member 29 of the feeler device, and the other member 31 of which is connected by means of a conductor 30 with the other side of the secondary winding of the transformer.

Pivotally secured to the member 31 are gravity operated feeler fingers 32 between which and the member 29 the cloth passes, such cloth being indicated in dotted lines at X. This feeler device in its entirety is or may be similar to that shown in my prior patent above identified or in my copending application Serial No. 395,393, filed September 26, 1929.

I/Vhen it is desired to start the motor, the

push button 22 is depressed, thus closing a.

circuit at the point 16, 18 between the conductors 7 and 9. Current then'flows fronr the supply circuit 2 over conductor 6, through the electromagnet 5 and conductors 7 and 9 back to the other side of the supply circuit, thus energizing the magnet 5 and causing it to close the mainswitch. As soon as this switch is closed another circuit is established from the point 0 through the conductor 8, the primary of the transformer 10, conductor 11, contacts 12 and 12 and the armature 13, conductor 14 and contact 15, switch member 17 and the conductors 7 and 6, through the electromagnet 5, this circuit being normally closed and serving to maintain the energization of the electromagnet 5 after the circuit opens at the point 16, 18. Thus when the push button 22 is momentarily depressed and then released, the main switch 3 is closed by the magnet 5 and subsequently maintained closed by means of a holding circuit including the conductor 8, the relay contacts, and the switch member 17 When, therefore, it is desired to stop the motor, it-

is only necessary to depress push button 21, thus interrupting this holding circuit atthe point 15, 17. This de-energizes the magnet 5 and the spring 4 opens the main switch.

As long as the cloth passing through the feeler device is free from defects, such cloth serves to insulate the feeler fingers 32 from the member 29, and thus the circuit through the relay winding 26 is normally open. WVhen, however, any hole or loose end passes under any of the ieeler fingers 82, the circuit through the relay winding is automatically closed, current being supplied from the secondary of the transformer 10; The armature 13 is thus pulled over, thereby interrupt ing the holding circuit at the points 12, 12, and the main switch opened.

It will thus be seen that the holding circuit includes the primary winding of the transformer, the contacts or" the relay and a nor mally closed push button switch, and that I have provided another push button switch controlling a wholly independent circuit by means of which the main switch may be closed after it has been opened. It will holding said switch closed, a circuit including a relay for normally maintainingjsaid electromagnetic means energized and said switch closed, and automatic means responsive to abnormal conditions for causing said relay to interrupt said last mentioned circuit and thus permit said switch to open.

2. In an automatic stop system for electrically driven machines, the combination with an electric motor and supply circuit therefor, of switch in said circuit biased to open position, electromagnetic means for closing said switch and holding it closed, a normally closed circuit, including a. relay, for maintaining said electromagnetic means energized and said switch closed, automatic means responsive to abnormal conditions for causing said relay to interrupt said normally closed circuit, and manual means,- independent of said relay, for restoring the circuit through said electromagnetic means.

trically driven machines, the combination with an electric motor and supply circuit therefor, of a switch in said circuit biased to open position, electromagnetic means for closing said switch and holding it closed, a normally closed circuit forv maintaining said electromagnetic means energized and said switch closed, automatic means responsive to the like, the combination with an alternating current motor and a supply circuit therefor,

of a switch in said circuit biased to open position, electromagnetic means for closing sald switch and holding it closedfa feeler.

device through which the cloth passes, a transformer, a circuit connecting said feeler device with the secondary of said transformer, a relay having a winding included in said secondary circuit, and having contacts controlled by said winding, and a normally closed circuit tapping said supply circuit and including in series said electromagnetic Y 3. In an automatic stop system for elecmeans, the primary of said transformer and the contacts of said relay.

5. In an automatic stop system for elec trically driven cloth finishing machines and the like, the combination with an alternating current motor and a supply circuit therefor, of a switch in said circuit biased to open position, electromagnetic means for closing said switch and holding it closed, a feeler device through which the cloth passes, a transformer, a circuit connecting said feeler device with the secondary of said transformer, a relay having a winding included in said secondary circuit, and having contacts controlled by said winding, a normally closed circuit tapping said supply circuit and including in series said electromagnetic means, the primary of said transformer, and the contacts of said relay, and a manually operated switch also in said normally closed circuit.

In testimony whereof I afiix my signature.

VANDER B. LOWDER. 

